Scanning distance measurement apparatuses have been proposed, which measure distances to measurement targets with laser light and which are also called laser radar apparatuses. A typical distance measurement apparatus includes a light transmitting unit that performs two-dimensional scanning with laser light (or laser pulses) from, for example, a laser source that emits the laser light at predetermined intervals using a micro electro mechanical system (MEMS) mirror or the like and radiates the laser light. The distance measurement apparatus also includes a light receiving unit that detects light reflected from the measurement target with a photodetector in the scanning with the laser light by the light transmitting unit to calculate the distance from each scanning position to the measurement target.
Since, for example, raster scan is performed in which a scan angle range is scanned with laser light deflected with a mirror, the interval between sampling points (or focusing points) (hereinafter also referred to as a “sampling density”) with the laser light is fixed within a measurement range with respect to a point a distance from the distance measurement apparatus. The sampling density with the laser light in the measurement range is increased with the decreasing distance from the distance measurement apparatus and is decreased with the increasing distance from the distance measurement apparatus. This is because, although a predetermined number of the sampling points are set in the measurement range, the measurement range is widened with the increasing distance from the distance measurement apparatus and is narrowed with the decreasing distance from the distance measurement apparatus.
The distance measurement apparatus is also applicable to detection of a living body, such as a human being, and an object, such as a vehicle. The distance measurement apparatus is capable of detecting an athlete, such as a gymnast or a basketball player, to measure the form of the athlete (for example, the form of a gymnastic performance or the form of a shoot of the basketball) or the like. The form or play of an athlete is capable of being analyzed based on the form measured by the distance measurement apparatus in the above manner.
In a case in which the measurement target is remote from the distance measurement apparatus, the measurement range is widened and the case is appropriate for, for example, detection of a play of a gymnast that is remote from the distance measurement apparatus. However, since the sampling density with the laser light is decreased, it is difficult to perform the measurement with high resolution. In addition, since the size of the measurement range and the sampling density are varied with the distance from the distance measurement apparatus to the measurement target, it is difficult to stably perform the measurement with high precision. For example, in a case in which the measurement target is close to the distance measurement apparatus and the measurement range is narrow, when the measurement target moves outside the measurement range even if the sampling density is high, the distance to the measurement target is not capable of being measured to reduce the measurement precision.
In contrast, setting the sampling density to a high value in order to perform the measurement with high resolution when the measurement target is remote from the distance measurement apparatus makes the sampling density when the measurement target is close to the distance measurement apparatus very high. In this case, since the light-emitting frequency is very high, the number of times of light emission from the laser source is increased to increase power consumption. As a result, for example, heat emission from the laser source may occur and the light emission is liable to be unstable. Accordingly, it is difficult to perform the measurement with high resolution when the measurement range is wide.
As examples of the related art, Japanese Laid-open Patent Publication No. 2014-119428 is known.